The present invention relates to a printing apparatus and a print control method. More particularly, the present invention relates to a printing apparatus having a printhead and a buffer memory for storing image data, and a print control method for transferring image data stored in the buffer memory to a printhead and printing an image on a print medium.
In a conventional print operation of a so-called serial printer, at least one buffer memory is employed to store image data for an image area printed by a single scan of a printhead, and an image is printed on a print medium by transferring the image data directly from the buffer memory to the printhead (hereinafter, such buffering method will be referred to as "scan-based buffering"). Moreover, in a case of using a color printer comprising a printhead, in which a plurality of head units are each provided for respective colors, and have the same number of pixels (same print width), are arrayed in the scanning direction, the similar scan-based buffering is employed.
Because of large-scale integration of logical circuits and downsizing of a printhead, the latest printers employ a printhead in which a plurality of head units corresponding to respective colors are arrayed in a line in the print paper conveyance direction. In the printer employing such a printhead, the positions of dots, printed each time the printhead is scanned, are different for each color with respect to the print paper conveyance direction. Therefore, buffer memory management becomes complicated in the aforementioned scan-based buffering. In view of this, complications buffer memories having different sizes are provided for each of the colors, and a method (hereinafter referred to as "scroll buffering") where a buffer controller scrolls the buffer memories corresponding to each color is employed.
However, the scan-based buffering is limited in terms of its application depending on the type of the printhead as described above. For instance, the scanbased buffering is difficult to apply to a printhead whose plural head units corresponding to respective colors are arrayed a in line in the print paper conveyance direction. Meanwhile, in the scroll buffering, since buffers are fixedly provided for respective colors, for instance, in a case where image printing is performed by using black only, buffers provided for other colors are wasted. Thus, it raises a problem of inefficient usage of buffer memories.
Furthermore, multi-pass printing for printing an image by scanning a printhead for the same area plural times has a disadvantage of complicated control. Moreover, since the conveyance amount of the print medium must be constant for each scan of the printhead, the print speed cannot be increased.